Which buffer system is the primary one in the human body?

• A. Phosphate buffer system
• B. Bicarbonate buffer system
• C. Protein buffer system
• D. Ammonium buffer system

Answer: (B)

The bicarbonate buffer system is the primary buffer system in the human body, playing a crucial role in maintaining acid-base homeostasis. This system regulates pH by balancing the levels of carbonic acid (H2CO3) and bicarbonate ions (HCO3-) within the blood. When an excess of hydrogen ions (H+) is present, bicarbonate can react to neutralize them, forming carbonic acid, which can then be converted to carbon dioxide and exhaled through the lungs, effectively removing acid from the body.

Conversely, if the body becomes too alkaline, carbonic acid can dissociate to release hydrogen ions, thereby lowering the pH back toward normal levels. This immediate response to pH changes underscores the importance of the bicarbonate system in everyday physiological function.

Other buffer systems, such as the phosphate buffer system and protein buffer system, also contribute to pH regulation but are more relevant in specific contexts, such as intracellular fluid and protein metabolism, respectively. The ammonium buffer system is less prominent in terms of overall impact on physiological pH in the human body, further emphasizing the bicarbonate buffer system's crucial role.